尿激酶活性测定方法的比较

根据中国及日本药典,对测定尿激酶活性的两种方法的灵敏度和重复性进行了考察对比,对不同样品测定结果进行了比较。     

Shear modulus of sintered 'house of cards'-like assemblies of crystals

A cell model of a 'house of cards'-like assembly of crystals is used for the study of the evolution of the shear modulus during sintering. The crystals are assumed to have a lozenge shape. The cell model takes different crystal-crystal contacts into account. The force needed to separate two sintered crystals is calculated using the minimum surface area (MSA) approximation. By varying the thickness, long axis, and short axis of the crystals, it is possible to make space-filing configurations which have a nonzero shear modulus at crystal volume fraction that can be as low as phi = 0.03. This is significantly lower than the volume fractions phi > 0.52 that are found in studies where the MSA approximation is applied to assemblies of spherical particles. It is found that sintering may cause a nonlinear volume fraction dependence of the shear modulus, which depends on the shape of the crystals, the type of crystal-crystal contacts, and the character of the crystal assembly. The calculated shear modulus is analyzed using the phenomenological expression (phi - phi0)beta, where phi0 represents the volume fraction at the start of sintering. The exponent beta is found to vary between 1 and 2. The interpretation of the shear modulus using a fractal model is also discussed.     

Study of the influence of concentration on the time for first appearance of crystallization of polyethylene from xylene

An experiment is reported in which a simple laser light-scattering technique is used to measure the time for a critical turbidity to appear during the crystallization of polyethylene in xylene. The effect is examined over the entire range of solution concentration, and it is found that the relation between this concentration and temperature is linear for all solutions, provided that the time for turbidity to develop is arranged to be the same in all cases. In the appendix it is reasoned that similar results could have been obtained if, instead, times had been measured to a given degree of crystallinity rather than of turbidity. Departures from this linearity at low concentrations are taken as indicating multimolecular nucleation for all concentrations greater than about 1%.     

Experimental and theoretical studies of asymmetry of transport properties of modified ultrafiltration membranes

Ultrafiltration membranes based on polyamide and polysulfone modified by polyelectrolytes are produced. The effect of the nature of a polymer matrix and modifier on the rejection ability and diffusion permeability of membranes is studied. The effect of the asymmetry of transport properties, which is manifested at different orientations of membrane with respect to the flow of electrolyte, is quantitatively evaluated. It was demonstrated that the asymmetry of substance transport is more pronounced in the ultrafiltration regime than in the diffusion of sodium chloride solutions. A mathematical model that describes the filtration of binary electrolyte solutions on partially charged two-layer membranes is proposed and the corresponding boundary-value problem is solved analytically. The qualitative correspondence between theoretical calculations and experimental data on the asymmetry effect of the rejection ability of two-layer system is revealed.     

Milestones of the development of kinetics of electrode reactions

The birth and the development of the kinetics of electrode processes?Cmostly focusing on the case of the hindered charge transfer step and the early period?Care reviewed. It is shown how this important branch of electrochemistry was established and how and why the ideas of chemical kinetics have been introduced in electrochemistry. The history of electrode kinetics represents a good example for the progress of science in general, since it can be followed how the experimental observations conduce to the development of theory and how the theory influences further research. It is also demonstrated that the acceptance of new ideas is a thorny path. An attempt is made to acknowledge the merit of the scientists whose experimental or theoretical contributions brought paradigmatic changes in the thinking about the nature of electrode processes. In this context, the appropriate naming of equations is also discussed by using the example of the Erdey-Grúz?CVolmer vs. Butler?CVolmer equation. A discussion concerning the present trends is also included, which perhaps may predict the near future. A longer prognosis is avoided since the history of science teaches us that the real breakthroughs could not be predicted.     

Effect of form of reagent on particle sizes of precipitates

The particle size of an ionic precipitate is much smaller when one of the reactants is introduced as a solid rather than as a solution The effect is enhanced as the particle size of the solid reagent is decreased. The presence of a freshly dissolved inert electrolyte also influences the particle size of a precipitate The affects are not attributable merely to the degree of supersaturation but rather to the provision by the freshly dissolved material of sites upon which nucleation can be induced.     

渣油悬浮床加氢水溶性催化剂预硫化研究 Ⅱ 钼酸盐硫化产物的XPS分析

通过XPS分析法对钼酸盐的硫化行为进行了考察,分别考察了四价钼物种质量分数和硫钼元素的质量分数比，发现硫化产物的表面化学组成中四价钼质量分数和硫钼元素质量分数比不成正比，证实了该产物表面钼的硫化物不完全以MoS2形式存在。未经过临氢加热的硫化产物表面的四价钼物种的质量分数显著低于经过临氢加热的样品的质量分数，说明临氢加热在钼酸盐的硫化过程中起了重要作用。氯化铵是钼酸盐硫化过程中有效的助硫化剂，当它的用量增大时，硫化产物表面四价钼的质量分数也增大。以蒽为探针，使用化学探针法测定了硫化产物在渣油加氢过程中的催化活性，发现随着氯化铵用量的增加，产物的催化活性也相应提高，印证了XPS测定结果。     

Theoretical methods of investigation of excited states of organic molecules

A brief review of quantum-chemical methods applied to describe excited states of organic molecules is presented. The main emphasis is put on advantages and disadvantages of widely used computational techniques. A brief summary of the performance of such methods and practical recommendations on their use is included.     

解决能源问题的新途径——光解水制氢的研究

面对日益枯竭的能源危机,氢能是一种洁净、最有前景的替代能源。目前在各种制氢的方法中光催化分解水制氢的研究最多,光解水过程中催化剂最关键,本文对利用太阳能光解水的途径、提高光催化反应效率以及光催化剂的开发研究进行了综述。     

Thermodynamic parameters of solvation of nonelectrolytes in aqueous solutions of amides of carboxylic acids

Interaction and reorganization contributions to solvation enthalpies of nonelectrolytes in aqueous solutions of amides of carboxylic acids with different degree of N-substitution and N-methylpyrrolidone are calculated. The data are discussed using structurally thermodynamic characteristics of water-amide systems obtained by us previously. It is found that the type of concentration dependence of the solvation enthalpy of nonelectrolytes in all solutions investigated is determined by the type of reorganization component. It is shown that the highest solvation exothermicity of nonelectrolytes in water is due to the lowest value of the reorganization contribution in spite of that nonelectrolytes interact weaker with water than with non aqueous components.     

Effect of pretreatment of molasses and posttreatment of fermented broth in industrial production of ethanol

The aim of preclarification is to minimize sludge going to yeast separators. This purpose is partially fulfilled. However, it has been measured during the plant trial runs that preclarification does not noticeably improve fermentation. The aim of postclarification is to minimize sludge going to distillation. This purpose is well served as noted from the fact that cycle run of distillation columns using postclarification is three times longer (9–12 mo) as compared to the normal one (3–4 mo).     

Calculation of the efficiency of purification by crystallization of ideal multicomponent stereoisomeric mixtures

A method for evaluating the maximum theoretical recovery of pure component from a stereoisomeric mixture by crystallization is discussed. The approach is based on the approximation of ideal behaviour as exemplified by the Schroeder–van Laar equation for conglomerates, and the Prigogine–Defay equation for racemic compounds. These equations are used to calculate the n-dimensional eutectic. It is shown that the n-dimensional eutectic is more soluble than the (n−1)-dimensional eutectic. A calculation is performed which removes only the n-dimensional eutectic from the sample and calculation of recovery through this discrete purification step is possible. After this, a system of n−1 components is obtained. The calculation may be repeated until only one component remains. The overall recovery of pure isomer is the product of the recoveries at each discrete purification step. The procedure is well suited to computer algorithm and a summary listing is presented. A series of example calculations are included for reference purposes. The methodology is intended to be useful in guiding efforts to improve process economics.     

镀锡板镀层测试

以８０９８单片机作智能部件研制开发的对镀锡板度测试装置，采用ＳＴＤ标准总线结构，汉字菜单提示，人－机对话方式操作，采用电解剥离法检测电位跃变曲线，根据电流和起始时间计算出镀层厚度，可直接显示，打印测试曲线和分析结果。     

Investigation of some modes of flat-bed chromatography

A comparison of different chromatographic methods is presented: column liquid chromatography (CLC), thin layer chromatography (TLC), and continuous-elution flat-bed chromatography (CEFBC), which is in fact a combination of the first two methods. In CEFBC a sample is applied to a sorbent layer in a steady flow of eluent, and the components are detected directly on the layer, or immediately upon leaving it, during the separation process. It is shown that evaluation of the separation processes in CEFBC is best accomplished in terms of the parameters applicable in CLC. The reproducibility of the analytical results obtained by CEFBC is better than in the case of TLC by a factor of 6 to 10, and approaches that known for CLC.     

掺杂剂对聚乙炔性质影响的理论研究

以多烯烃模拟聚乙炔链,用CNDO/2方法讨论了各种掺杂剂对聚乙炔性质的影响,掺杂剂使孤子宽度收缩变窄,且p型掺杂剂比n型掺杂剂的影响更大,掺杂剂影响聚乙炔链中的电荷密度波,使电荷主要集中分布于掺杂剂附近的碳原子上。掺杂碱金属时,掺杂剂原子的最高占据轨道与聚乙炔中孤子自旋轨道之间的作用由Li到K依次增强,解释了ESR实验结果。     

The heterometric microdetermination of mercury of mercaptobenzthiazole

The heterometric determinations of murcury or mercaptobentlnazole are very sensitive reactions. An aqueous or a dilute alcoholic solution is used and the titration may lie carried out at pH 2–10. If meicaptobenzlhiazole is determined, two analytical end-points are obtained : the first gives an estimate, the second gives the precise end-point. In all cases, the insoluble Hg(MBT)₂ is obtained, The presence of larger amounts of strong acids is disadvantageous Large amounts of acetic acid cause distuibances in aqueous solution; dilute alcoholic .solution is therefore used The theoretical end-point is obtained by the intersection of two lines. In acid solution a horizontal maximum density line is obtained at the end ot the reaction, in alkahne solution a maximum point is obtained instead. 1–2 mg mercury or meicaptobenzthiazole may be determined in 20–30 ml solution with an error of 0–3% 'Ihe titration time is 10–20 mniutes     

Sorption and desorption of water vapor by grains of native starch of some crops

The sorption-desorption of water vapor by grains of potato, corn, and wheat native starch is studied. It is shown that water vapor is mainly sorbed inside starch grains. A model is proposed for water vapor sorption by starch grains. Constructed sorption isotherm is shown to adequately describe the process in a wide humidity range. The kinetics of the sorption and desorption of water vapor by starch grains is shown to have an abnormal character.     

Infrared determination of traces of sulfate in reagent chemicals

A method for determining traces of sulfate in reagent-grade chemicals is presented. The sample is passed through an alumina column in acid solution to isolate the sulfate, which is then eluted with ammonia. Potassium bromide is added to an aliquot of the eluate, and the solution is freeze-dried. The resulting powder is pressed into a disk whose infrared spectrum is recorded. The method is reasonably accurate and requires a minimum of operator time per sample because a large number of samples can be processed together     

Theoretical study of mechanism and selectivity of copper-catalyzed C-H bond amidation of indoles

Density functional theory calculations are used to study the reaction mechanism and origins of C2 selectivity in a copper(I)-catalyzed amidation of indoles. It is shown that concerted metalation-deprotonation is not able to reproduce the observed regioselectivity. Instead, an unprecedented mechanism based on a four-center reductive elimination is proposed to be responsible for the reaction outcome. This mechanism has a lower reaction barrier and is able to reproduce the experimentally observed selectivity. A possible alternative mechanism involving a Cu(II) species instead of Cu(III) is presented, but it is shown that higher energy barriers are associated with this mechanism. An important technical detail is that addition of dispersion effects to the B3LYP results is necessary to reproduce the observed selectivity, although not important for the overall mechanistic proposal.